Spring is used under impact, vibration or long-term alternating stress, so spring steel is required to have high tensile strength, elastic limit and high fatigue strength. In terms of technology, it is required that the spring steel has certain hardenability, is not easy to decarburize, and has good surface quality. That is, it is a high-quality carbon structural steel with a carbon content of 0.6% - 0.9%. Alloy spring steel is mainly silicon manganese steel, and their carbon content is slightly lower, mainly by increasing silicon content Wsi to improve properties; In addition, there are chromium, tungsten and vanadium alloy spring steels. In recent years, in combination with China's resources and according to the requirements of new technologies for automobile and tractor design, a new steel grade with boron, niobium, molybdenum and other elements added on the basis of silicon manganese steel has been developed, which extends the service life of springs and improves the quality of springs.
Spring performance requirements of Huamao Spring Factory
Spring is used under impact, vibration or long-term alternating stress, so spring steel is required to have high tensile strength, elastic limit and high fatigue strength. In terms of technology, it is required that the spring steel has certain hardenability, is not easy to decarburize, and has good surface quality. That is, it is a high-quality carbon structural steel with a carbon content of 0.6% - 0.9%. Alloy spring steel is mainly silicon manganese steel, and their carbon content is slightly lower, mainly by increasing silicon content Wsi to improve properties; In addition, there are chromium, tungsten and vanadium alloy spring steels. In recent years, in combination with China's resources and according to the requirements of new technologies for automobile and tractor design, a new steel grade with boron, niobium, molybdenum and other elements added on the basis of silicon manganese steel has been developed, which extends the service life of springs and improves the quality of springs.
Production process
Generally, spring steel can be produced by electric furnace, open hearth furnace or oxygen converter; High quality spring steel with good quality or special properties is made by electroslag furnace or vacuum furnace. The specified content range of carbon, manganese, silicon and other major elements in spring steel is narrow, so the chemical composition must be strictly controlled during smelting. When the silicon content is high, it is easy to form bubbles and other defects, and when the ingot is not cooled after forging and rolling, it is easy to produce white spots. Therefore, the raw materials for smelting must be dry, gas and inclusions must be removed as far as possible, and overheating of molten steel must be avoided. Special attention shall be paid to decarburization and surface quality of spring steel during rolling. When the steel surface is seriously decarburized, the fatigue limit of the steel will be significantly reduced. For high silicon spring steel such as 70Si3MnA, attention should be paid to avoid graphitization. Therefore, the stop rolling temperature during hot working shall not be too low (≥ 850 ℃) to avoid staying too long in the temperature range (650~800 ℃) where graphitization is easy to form. After the spring is made, shot peening can make the surface layer of the spring produce residual compressive stress to offset part of the working stress on the surface layer and inhibit the formation of surface cracks, which can significantly improve the fatigue limit of the spring.
